It was, by all accounts, one of the best bashes of the Oscars season. Yet one of the guests at the lavish Hollywood soiree hosted by De Beers, the world’s biggest diamond company, had more on his mind than the array of cocktails and film stars at a Sunset Boulevard hotel.

Festus Mogae, former president of Botswana, was on a mission to rekindle demand for the precious stones on which his country’s wellbeing depends.